The common belief that has prevailed for the last 10 years is that Neanderthal DNA lives on in modern humans, particularly Europeans and Asians. However, there is not much known about the connection between this archaic ancestor and modern day Africans.

While Neanderthal ancestry has largely been associated with Europeans and Asians, a new study reveals that an unexpectedly large amount of this ancestral DNA prevails in modern populations in Africa. It also suggests that much of this DNA came from Europeans who migrated back into Africa from 20,000 years ago.

According to Michael Petraglia, anthropologist at the Max Planck Institute for the Science of Human History, the study establishes that gene flow with Neanderthals exists in all modern humans. It may also help explain why East Asians appear to have more Neanderthal ancestry than Europeans.

Some 70,000 years ago, Homo sapiens migrated from Africa into Eurasia and there intermingled with Neanderthals. It was previously believed that Neanderthal DNA was present in African populations but only in insignificant amounts, as opposed to 2% of modern DNA among Europeans and East Asians.

Joshua Akey, an evolutionary biologist from Princeton University, and his team compared the genome of a Neanderthal from Altai region in Siberia against 2504 modern genomes uploaded to the 1000 Genomes Project, which is a genome catalog that includes 5 African subpopulations. The team then calculated the probability that each stretch of DNA was inherited from a Neanderthal ancestor.

The researchers discovered that, on average, African individuals inherited 0.3% of their genome from Neanderthals, which is significantly more than previously believed. They also found that these included genes that protect against ultraviolet radiation and boost immune function.

These findings suggest that half of the Neanderthal DNA came when Europeans migrated back into Africa. The team also theorizes that the DNA shared by modern Africans and the Altai Neanderthal might not be Neanderthal but a residue DNA of early humans retained in both Eurasians and Africans which was then picked up by Neanderthals.

The study done by Akey and his team may also help explain why East Asians have 20% more Neanderthal DNA than Europeans when Neanderthal remains have been found in Europe. Considering the theory that Europeans introduced Neanderthal sequences into Africa, the previous assumption that did not take into account the Neanderthal sequences shared by Africans and Europeans will be corrected. Once corrected, there will be similar amounts of Neanderthal DNA shared by Europeans and Asians.

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